Preheat the oven to 180'C.
Mix together the egg whites, icing sugar, flour, ground almonds and the powdered green tea.
Melt the butter until it is deep nut colour - to ensure that the butter does not burn, pay attention to the sizzling: when it quiets down, the butter is ready. Mix in the dry ingredients.
Butter your financier moulds then fill with the financier batter. Sprinkle the sea salt and the sesame seeds over the top and then bake in the oven for 15-20 minutes.
Allow to cool before removing from the moulds to serve.
For the ganache:
Bring the double cream to the boil, and remove from the heat. Pour the white chocolate into the cream, and let sit for 2 minutes before stirring into a smooth and shiny sauce. Set aside until needed.
«The ganache should be kept at room temperature. If it becomes too firm, gently warm it over a double-boiler.»